Update RelativeHeading.java to handle movement.
+ added consumeFuel() to Plane.java, to calculate fuel consumption every tick, according to speed.
+ added field speed to Plane.java, to hold basic speed, for simple calculations
+ added getLength() to Vector2d.java
adds spawnPlane() method, which spawns planes from entry points randomly.
method call needs to be placed in a place, where it would be called each tick
Spawns plane pseudo randomly in time interval between min and max
removes prints to console
adds airport, just for reference.